Microwave oven construction



March 7, 1967 VEL N 3,308,261

MICROWAVE OVEN CONSTRUCTION Filed May 4, 1964 2 Sheets-sheet l g k I l March 7, 1967 Filed May 4, 1964 2 Sheets-Sheet 2 Zeonard Y/eZan der United States Patent 3,308,261 MICROWAVE OVEN CONSTRUCTION Leonard Velander, Minneapolis, Minn., assignor, by mesne assignments, to Litton Precision Products, Inc., Beverly Hills, Calif., a corporation of Delaware Filed May 4, 1964, Ser. No. 364,377 3 Claims. (Cl. 219-1055) This invention relates to microwave ovens and, more particularly, to an improved microwave oven construction having novel means for cooling the source of highfrequency energy to the cooking enclosure and for ventilating the cooking enclosure to prevent formation of condensation therein.

Microwave ovens of the type generally utilized commercially comprise a housing having a cavity therein which is supplied with energy from a suitable source of microwaves such as, for example, a magnetron. The body to be heated or cooked is placed in the cavity and upon energization of the magnetron will be heated or reconstituted in a relatively short time.

As the magnetron generates a relatively large quantity of heat in use, suitable cooling means such as a blower have been utilized to cool the magnetron.

It has been found in use that undesirable condensation often formed in the cooking cavity. To remove such condensation, it was proposed that a separate fan or blower be used to ventilate the cooking enclosure. The fan was adapted to blow air through the cooking cavity. The use of two fans, one for cooling the magnetron and the second for ventilating the cooking enclosure, was costly.

An object of this invention is to provide an improved microwave oven wherein the disadvantages and deficiencies of prior constructions are obviated.

Another object of this invention is to provide an improved microwave oven having first duct means therein adapted to be connected at one end to a source of pressurized air and at the other end being adapted to exhaust air to the exterior of such oven, and second duct means communicating the cooking cavity in the oven with the first duct means for aspirating air from the cooking cavity.

A further object of the present invention is to provide an improved microwave oven having a single blower for effectively cooling the magnetron supplying high-frequency energy to the cooking cavity and for aspirating air from the cooking cavity within the microwave oven, thereby preventing build up of undesirable condensation in the cooking cavity.

The foregoing and other objects and advantages of the invention will be best understood from the following description of a presently preferred embodiment thereof, reference being had to the accompanying drawing, wherein like numerals refer to like elements, and wherein:

FIGURE 1 is a front elevation view of a microwave oven embodying the present invention, with parts being broken away for clarity; and

FIGURE 2 is a cross-sectional view of the microwave oven taken generally along the line 2-2 of FIGURE 1.

Referring to FIGURES l and 2, there is illustrated a microwave oven comprising a casing or housing 12 having an access door 14 pivotally aflixed on the front thereof. The access door may be opened upon actuation of handle 15.

Within the housing 12 is a hollow generally rectangular metallic enclosure or cavity 18 which may have mutually perpendicular top, side and bottom walls. The dimensions of the cavity are preferably, although not necessarily, large compared with the wave length of the magnetron at the operating frequency.

Supported by brackets 20 within the enclosure 18 is a shelf 22 for supporting the load to be heated or re- "ice 2 constituted. It will be understood that when the handle 15 on the door 14 is actuated to open the access door, entry will be provided into the enclosure or cooking cavity 18 to allow for insertion or removal of a load therefrom.

The housing 12 is adapted to be suitably supported on a support surface by means of adjustable support screws or legs 24.

The means for supplying microwave energy to the enclosure 18 for heating the body or load therein is preferably a magnetron 26. The magnetron is supported within the housing and the top thereof extends through an opening 28 in the bottom wall of the enclosure 18. It is seen that the magnetron 26 is adapted to radiate highfrequency energy upwardly into the enclosure 18.

Provided in the enclosure and continuously movable therein is a deflector 30. The deflector 30 preferably comprises a circular plate member aflixed to shaft 32 which is driven by suitable motor means 34 carried on the top of the enclosure 18 within the housing 12. The planar deflector 30, which lies in a plane at an angle with respect to the axis of rotation of the shaft 32, functions to deflect the high-frequency energy and to produce a more uniform heating of the body or load to be cooked carried on the shelf 22 within the enclosure 18.

Means are provided within the housing 12 of the microwave oven for dissipating the heat generated by the magnetron 26. Such means may comprise ducts 36, 39 and 40. The duct 36, which may be formed from sheet metal, is disposed about the magnetron and is connected at one end to a.source of pressurized air 38, which may be a centrifugal blower, and at the other end to a duct 40 for exhausting air to the exterior of the casing 12. Duct 39, which is preferably a flexible hose directs air from the housing of fan means 38 to the interior of the magnetron housing. Suit-able connectors 41 and 42 are provided to connect the duct 36 to the housing of the fan means 38 and to an end of the duct or conduit 40. Preferably, duct 40, made from sheet metal, is insulated as indicated generally at 43. The insulation may have a vapor barrier on the exterior thereof.

Adjacent to the exhaust end 50 thereof, the conduit 40 communicates with the interior of the enclosure 18 via a passageway 44. The passageway 44 comprises a conduit which communicates atone end with the opening 46 in the top wall of the enclosure 18 and at the other end with the opening 48 defined in the conduit 40. A baffle 50 is disposed in the conduit 40 and may be formed by a portion struck from a wall thereof. The baffle 50 restricts the conduit 40 adjacent to the opening 48 and thereby increases the velocity of the air discharging therefrom to enhance the aspiration of air from within the enclosure 18 through the passageway 44 and out the opening 52 at the end of the conduit 40.

On the front of the microwave oven 10 is a control panel 56 having a plurality of control buttons 57 thereon for selecting a predetermined timing cycle for the oven. Disposed above the push buttons 57 are a pair of indicator lights 58 and 60. The light 58 is indicative that the oven is ready for operation and the light 60 indicates that the oven is cooking.

As seen in FIGURE 2, there is provided within the casing 12 a transformer 62 for supplying the power requirements of the magnetron. The transformer is connected to a source of current in the usual manner.

It will be noted that the door 14 is provided with a seal 64 for preventing the egress of high-frequency energy from the cavity 18. It is noted that the top and bottom of the access door extend substantially beyond the seal means between the door and the entrance to the cavity 18 for assuring that there is no escape of the high-frequency energy from the cavity 18 directly into the surrounding ambience.

The front of the microwave oven may be provided with an accessory door 66 which is pivotally secured at the bottom thereof to the casing 12.

The present invention provides an improved microwave oven having a single blower means therein for effectively cooling the magnetron and for aspir-ating air from the cooking cavity within the microwave oven, thereby preventing build up of undesirable condensation in the cooking cavity. The desired cooling of the magnetron and ventilating of the cooking cavity by means of a single blower provides a compact microwave oven construction and one which is less expensive than previous designs.

While there has been shown and described a specific embodiment of the present invention, it will of course be understood that various modifications and alternative constructions may be made without departing from the true spirit and scope of the invention. Therefore, it is intended by the appended claims to cover all such modifications and alternative constructions as fall within their true spirit and scope.

I claim:

1. A microwave oven comprising a housing having a metallic enclosure therein, means for supplying high frequency energy into said enclosure, said enclosure being adapted to support a load to be heated therein, means for cooling said supplying means comprising blower means for providing an air stream, first duct means within the housing connected to said blower means and to the housing for conveying an air stream past said supplying means to the exterior of said housing, and second duct means connected between said enclosure and said first duct means downstream from said supplying means responsive to the passage of an air stream in said first duct for aspirating air and vapor from said enclosure into said first duct, whereby the build-up of condensation within said enclosure is prevented by exhausting it to the exterior of the housing.

2. A microwave oven as described in claim 1 further comprising baflle means connected proximate the juncture of the first and second ducts for increasing the velocity of air passing in the first duct at the location of the connection between the first and second ducts to enhance the aspiration of air from said enclosure.

3. A microwave oven as in claim 1 wherein said second duct means is connected to said first duct means adjacent the end proximate its connection to the housing thereof.

References Cited by the Examiner UNITED STATES PATENTS 3,127,495 3/1964 Polries et a1 2l910.55

FOREIGN PATENTS 941,434 11/1963 Great Britain.

ANTHONY BARTIS, Primary Examiner.

RICHARD M. WOOD, Examiner.

L. H. BENDER, Assistant Examiner. 

1. A MICROWAVE OVEN COMPRISING A HOUSING HAVING A METALLIC ENCLOSURE THEREIN, MEANS FOR SUPPLYING HIGH FREQUENCY ENERGY INTO SAID ENCLOSURE, SAID ENCLOSURE BEING ADAPTED TO SUPPORT A LOAD TO BE HEATED THEREIN, MEANS FOR COOLING SAID SUPPLYING MEANS COMPRISING BLOWER MEANS FOR PROVIDING AN AIR STREAM, FIRST DUCT MEANS WITHIN THE HOUSING CONNECTED TO SAID BLOWER MEANS AND TO THE HOUSING FOR CONVEYING AN AIR STREAM PAST SAID SUPPLYING MEANS TO THE EXTERIOR OF SAID HOUSING, AND SECOND DUCT MEANS CONNECTED BETWEEN SAID ENCLOSURE AND SAID FIRST DUCT MEANS DOWNSTREAM FROM SAID SUPPLYING MEANS RESPONSIVE TO THE PASSAGE OF AN AIR STREAM IN SAID FIRST DUCT FOR ASPIRATING AIR AND VAPOR FROM SAID ENCLOSURE INTO SAID FIRST DUCT, WHEREBY THE BUILD-UP OF CONDENSATION WITHIN SAID EN- 